This application is based on Japanese Patent Application No. 10-269263 filed Sep. 24, 1998, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates in general to a roller turret, a method of manufacturing the roller turret, a roller turret cam index device, and a roller turret type rotary motion transmitting device, and more particularly to techniques for improvement of accuracy of pitch of rollers used in the roller turret.
2. Discussion of the Related Art
Generally, a roller turret includes a turret body rotatable about an axis thereof, a plurality of roller shafts provided on the turret body, and a plurality of rollers rotatably supported by the respective roller shafts. Each of the roller shaft includes a stud portion fitted in a mounting hole formed in the turret body, and a roller support portion which is concentric or coaxial with the stud portion and which supports the roller rotatably. The roller support portion of the roller shaft is disposed outside the turret body, so that the roller also disposed outside the roller is rotatably supported by the roller support portion.
Such a roller turret may be combined with a globoidal cam, a barrel cam, or a plate cam unit which is a combination of a plurality of plate cams (usually, two plate cams). The roller turret cooperates with the globoidal cam, the barrel cam and the plate cam unit, to constitute a globoidal cam index device, a barrel cam index device, and a parallel cam index device, respectively. The roller turret combined with the globoidal cam is generally called xe2x80x9ca roller gearxe2x80x9d. In the present application, the roller turret combined with the globoidal cam is referred to as xe2x80x9ca spur roller gearxe2x80x9d as distinguished from xe2x80x9ca face roller gearxe2x80x9d, which is the roller turret combined with the barrel cam. Those roller turrets are referred to as the spur roller gear and the face roller gear, in view of their similarity in configuration to a spur gear and a face gear. The roller turret combined with the plate cam unit, on the other hand, is referred to as xe2x80x9ca zigzag roller turretxe2x80x9d, in view of a pattern of arrangement of the rollers. The globoidal cam index device, the barrel cam index device and the parallel cam index device are collectively referred to as xe2x80x9ca roller turret index devicexe2x80x9d.
In the spur roller gear, the roller shafts are disposed on the turret body so as to extend in the radial direction of the turret body such that the axes of the roller shafts are perpendicular to the axis of rotation of the turret body. In the face roller gear and the zigzag roller gear, the roller shafts are disposed on the turret body so as to extend in the axial direction of the turret body such that the axes of the roller shafts are parallel to the axis of rotation of the turret body. The globoidal cam, the barrel cam and the plate cam units are collectively referred to as xe2x80x9ca roller turret camxe2x80x9d. Each of these roller turret cams includes a dwelling portion and an indexing portion with which the roller turret engages during rotation of the roller turret cam, so that the roller turret is held stationary while it is held in engagement with the dwelling portion, and is rotated while it is held in engagement with the indexing portion.
The spur roller gear is combined with a double enveloping worm to provide a spur roller gear type speed reducing device, while the face roller gear is combined with a cylindrical worm to provide a face roller gear type speed reducing device. Such a double enveloping or cylindrical worm has a thread which corresponds to a rib formed on the globoidal and barrel cams and which does not include a dwelling portion and therefore has a constant lead. A rotary motion of the worm at a constant speed will cause a rotary motion of the spur or face roller gear at a comparatively lower constant speed. The speed ratio of the spur or face roller gear with respect to the double enveloping or cylindrical worm can be increased to 1.0 by increasing the number of starts of the thread or tooth of the worm. In this case, the spur or face roller gear and the worm cooperate to constitute a spur or face roller gear type rotary motion transmitting device. Further, a spur or face roller gear type speed increasing device may be obtained where the spur or face roller gear is used as an input-side device while the double enveloping or cylindrical worm is used as an output-side device. The speed reducing device, rotary motion transmitting device (in a narrow sense) and speed increasing device, which have been described above, are collectively referred to as a rotary motion transmitting device in a broad sense. The spur roller gear type rotary motion transmitting device and the face roller gear type rotary motion transmitting device are referred to as a roller turret type rotary motion transmitting device. Where the roller gear type rotary motion transmitting device is used in combination with a drive device capable of rotating the worm (or roller gear) such that the worm is stopped at a desired angular position, the roller gear (or worm) can be stopped at a corresponding angular position.
In the conventional roller turret cam index device, it is difficult to improve the indexing accuracy of the roller turret, namely, the accuracy of stopping the roller turret at the desired angular position. Accordingly, the conventional roller turret type rotary motion transmitting device suffers from a problem of difficulty to improve the accuracy of rotary motion transmission (the accuracy of relative angular position of the roller turret and the worm). This difficulty is primarily due to difficulty to improve the accuracy of pitch of the rollers in the roller turret.
The mounting holes in which the roller shafts are partly received are formed in the turret body such that the roller shafts are equiangularly arranged and spaced apart from each other in the circumferential direction of the turret body. Even if the mounting holes are formed by machining with a high degree of accuracy of their positions, the mounting holes inevitably have an angular positioning error of about xc2x15 seconds. Usually, the stud portion of each roller shaft is press-fitted in the mounting hole with some amount of interference. Since the amount of interference is on the order of single-digit microns (xcexc), the roller shafts whose diameters of the stud portions have different amounts of deviation from the nominal value must be fitted in the appropriately selected mounting holes whose diameters also have different amounts of deviation from the nominal value. That is, the diameters of the stud portions of the roller shafts which have been produced are classified into a plurality of diameter groups. On the other hand, the diameters of the mounting holes formed in the roller turret are are measured. The combinations of the roller shafts and the mounting holes are determined so that the amount of interference between the stud portion of each roller shaft and the corresponding mounting hole is held within an optimum range. However, the matching of the diameters of the roller shafts with respect to the diameters of the mounting holes is a cumbersome procedure. Although the stud portion of the roller shaft may be fitted in the mounting hole with a clearance within a predetermined tolerance, this clearance fit is likely to deteriorate the accuracy of pitch of the rollers and reduce the strength of fixing of the roller shaft in the mounting hole. Alternatively, the stud portion of the roller shaft may be press-fitted in the mounting hole with a sufficiently large amount of interference, an excessively large amount of interference therebetween may lead to inclination or misalignment of the axis of the roller shaft relative to the centerline of the mounting hole, resulting in lowering of the accuracy of pitch of the rollers.
Further, it is impossible to establish a perfect alignment of the axis of the turret body about which the mounting holes are equiangularly spaced apart from each other by a machining operation on the turret body, with the axis of rotation of the end product, namely, the axis of rotation of the index device or rotary motion transmitting device. That is, the axis or center about which the mounting holes are equiangularly spaced apart from each other may more or less deviate from the axis of rotation of the turret body, and this deviation results in an angular positioning error of the mounting holes, and consequently causes deterioration of the roller pitch accuracy of the end product. If the turret body consists of a plurality of pieces which are fixed together, the misalignment or deviation of the two axes indicated above may be reduced to within about 2-3 microns. However, this solution is not satisfactory.
Further, the dimensional errors of the components associated with the rollers may also cause the roller pitch error of the roller turret. Where the roller is mounted on the roller support portion of the roller shaft via a needle bearing interposed therebetween such that the roller support portion and the roller respectively function as an inner race and an outer race of a roller bearing, for instance, a variation of the outside diameter of the roller support portion and variations of the inside and outside diameters of the roller will cause an error of the roller pitch of the roller turret. Therefore, it is required to minimize the overall diameter error of an assembly of the roller support portion, needle bearing and roller. However, the overall diameter error of that assembly cannot be actually reduced to a value smaller than 2-3 microns.
In addition, misalignment of the actual axis of rotation of the turret body with respect to the nominal axis due to inaccuracy of bearings used for rotatably supporting the turret body will cause the same result as if the roller turret had a roller pitch error. To avoid this problem, it is required to use high-precision bearings for supporting the turret body with high accuracy. In this case, the cost of manufacture of the roller turret assembly is undesirably increased. In some cases, the amount of misalignment cannot be sufficiently reduced even if expensive high-precision bearings are used for rotatably supporting the roller turret.
As described above, there are various causes for the roller pitch error of the roller turret. Each of the errors arising from the respective causes must be minimized. For instance, it is required to improve the accuracy of machining to form the mounting holes, the accuracy of mounting of the roller shafts on the turret body, and the dimensional accuracy of the components associated with the rollers. In this instance, however, the roller pitch error is still relatively large due to a cumulative error including the errors generated by the different causes. For instance, the roller turret of the roller turret cam index device inevitably suffers from an indexing error or angular positioning error of about xc2x110 seconds. Since the cost of manufacture of the roller turret progressively or exponentially increases with an increase in the required degree of accuracy, the roller pitch error of the roller turret cannot be further reduced at a practically acceptable cost.
The globoidal cam index device, barrel cam index device, spur roller gear type rotary motion transmitting device and face roller gear type rotary motion transmitting device have a further problem that the angular positioning or indexing accuracy is deteriorated due to vibration of the spur or face roller gear, which is generated due to a clearance or gap between the outer circumferential surface of the rollers and the rib of the globoidal or barrel cam or the thread of the worm. Each roller of the roller gear is moved in a groove defined by two portions of the rib of the globoidal or barrel cam or the thread of the worm, which two portions are spaced apart from each other in the axial direction of the cam or worm. To permit the roller to move in the groove in rolling contact with the mutually facing surfaces of the walls of the groove, it is necessary to provide a clearance between the surfaces of the walls and the outer circumferential surface of the roller. This clearance causes vibration or operating noise of the roller gear, which deteriorates the angular positioning or indexing accuracy and the rotary motion transmitting accuracy of the index device or rotary motion transmitting device.
It is therefore an object of the present invention to provide an inexpensive roller turret having a high degree of accuracy of pitch of its rollers.
Another object of the invention is to provide a roller turret cam index device including such a roller turret.
A further object of the invention is to provide a roller turret type rotary motion transmitting device including such a roller turret.
A still further object of the invention is to provide a method of manufacturing such a roller turret.
A yet further object of the invention is to provide a method of manufacturing such a roller turret cam index device.
Still another object of the invention is to provide such a roller turret type rotary motion transmitting device.
One of the objects indicated above may be achieved according to any one of the following modes of the present invention, each of which is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate possible combinations of technical features or elements within the principle of the invention. However, it is to be understood that the present invention is not limited to the following modes and combinations of the technical features.
(1) A method of manufacturing a roller turret which includes a turret body and a plurality of roller shafts each of which carries a roller rotatably mounted thereon, the method comprising: a step of preparing the turret body having a plurality of mounting holes formed therein such that the mounting holes are arranged in a rotating direction of the turret body; a step of preparing the plurality of roller shafts each including a roller support portion on which the roller is rotatably mounted, and a stud portion which is eccentric with respect to the roller support portion; a preliminary assembling step of preparing a preliminary roller turret assembly wherein each of the roller shafts is rotatably fitted at said stud portion in a corresponding one of the mounting holes; an angular pitch adjusting step of adjusting an angular pitch of adjacent ones of the plurality of rollers, by rotating the roller shafts; and a fixing step of fixing all of the roller shafts to the turret body body after the angular pitch adjusting step.
Examples of the roller turret manufactured by the method of the present invention include a spur roller gear, a face roller gear and a zigzag type roller turret, which have been described above. A roller turret type rotary motion transmitting device may be constituted by combining the spur roller gear with a double enveloping worm, or by combining the face roller gear with a cylindrical worm. These spur roller gear and face roller gear that are used in the roller turret type rotary motion transmitting device may be manufactured by the present method.
The turret body and the roller shafts may be manufactured by a manufacturer who assembles the roller turret, or by another manufacturer who does not manufacture the roller turret. In the former case, the xe2x80x9cstep of preparing the turret bodyxe2x80x9d and the xe2x80x9cstep of preparing the plurality of roller shaftsxe2x80x9d are considered to be a step of manufacturing the turret body and the roller shafts and thereby preparing these turret body and roller shafts. In the latter case, these two steps are considered to be a step of purchasing the turret body and the roller shafts and thereby preparing these turret body and roller shafts.
Since the stud portion and the roller support portion of each roller shaft are eccentric with respect to each other, rotation of the roller shaft will result in rotation of the axis of the roller support portion about the axis of the stud portion, so that the position of the axis of the roller support portion in the rotating direction of the turret body is changed. Accordingly, rotation of the roller shaft permits adjustment of an angular interval between the two adjacent rollers mounted on the corresponding two adjacent roller shafts one of which is rotated. In the roller gear, the xe2x80x9cposition of the axis of the roller support portion in the rotating direction of the turret bodyxe2x80x9d indicated above is, more precisely, the position of the axis of the roller support portion in a direction of tangency to the pitch circle of the rollers at the angular or circumferential position of the turret body at which the roller shaft in question is fixed. After the angular pitch adjusting step is completed, all of the roller shafts are fixed to the turret body so that the adjusted angular intervals between the adjacent rollers are maintained.
The angular pitch of the adjacent rollers is conveniently represented by an angle about the axis of rotation of the roller turret (turret body), which is defined by the axes of rotation of the two adjacent rollers. However, the angular pitch may be represented by a distance between the axes of the two adjacent rollers at a given axial position of the rollers on their axes (at a given radial position of the turret body, e.g., on the pitch circle of the rollers). In the present invention wherein the roller shafts having the mutually eccentric stud and roller support portions are rotated to adjust the angular pitch of the rollers, the axes of the roller support portions of all of the roller shafts do not lie on a single plane perpendicular to the axis of the roller turret, in a strict sense, where the roller turret is a spur roller gear. Where the roller turret is a face roller gear or a zigzag roller turret, the axes of the roller support portions of the roller shafts do not lie on a single circle having a center on the axis of the turret body. Therefore, if the angular pitch of the rollers is represented by the distance between the axes of the adjacent rollers, the actual distance does not accurately represent the angular pitch. Actually, however, the angular positioning or indexing accuracy of the spur roller gear in meshing engagement with a dwelling portion of a globoidal cam is not significantly influenced by a variation in the positions of the axes of the rollers in the axial direction of the turret body (spur roller gear). Similarly, the angular positioning or indexing accuracy of the face roller gear in meshing engagement with a dwelling portion of a barrel cam is not significantly influenced by a variation in the positions of the rollers in the radial direction of the turret body (face roller gear). Therefore, the variations in the positions of the rollers in the axial and radial directions of the turret body may be ignored. On the other hand, while the spur roller gear or face roller gear is in meshing engagement with an indexing portion of the globoidal cam (barrel cam) or a worm, the variations in the positions of the rollers in the axial direction of the turret body will significantly influence the angular position of the spur roller gear or face roller gear (hereinafter referred to as xe2x80x9croller gearxe2x80x9d), even when the positions of the rollers in the rotating or circumferential direction of the turret body remain unchanged. Therefore, the variations may not be ignored while the roller gear is in meshing engagement with the worm or the indexing portion of the globoidal or barrel cam. However, rotating the roller shafts will result in simultaneous change in the positions of the rollers of the spur roller gear in both of the axial and rotating directions of the turret body, and simultaneous change in the positions of the rollers of the face roller gear in both of the radial and rotating directions of the turret body. Accordingly, a change in the angular position of the spur roller gear or face roller gear due to changes change in the positions of the rollers of the roller gear in the axial and radial directions of the turret body may be considered to result from a change in the angular position of the roller gear due to changes in the positions of the rollers in the rotating direction of the turret body. Actually, the angular positions of the spur roller gear are adjusted by adjusting the positions of the rollers in the axial and rotating directions of the turret body, while the angular positions of the face roller gear are adjusted by adjusting the positions of the rollers in the radial and rotating directions of the turret body. Practically, however, this adjustment of the angular positions of the spur or face roller gear may be considered to be effected by only the adjustment of the positions of the rollers in the rotating direction of the turret body, that is, by only the adjustment of the angular pitch of the rollers.
The angular positions of the zigzag type roller turret in the parallel cam index device are determined by engagement of the two adjacent rollers with indexing portions in the form of cylindrical cam surfaces of two plate cams of a plate cam unit. In the zigzag type roller turret, the rollers are alternately located at two different positions in the axial direction of the turret body, so that the two adjacent rollers have different positions in the axial direction of the turret body. As in the case of meshing engagement of the spur roller gear or face roller gear with the worm or the dwelling portion of the globoidal or barrel cam, the position of the roller in the radial direction of the turret body as well as that in the rotating direction of the turret body is changed by rotation of the corresponding roller shaft. For the same reason explained above, the adjustment of the angular positions of the zigzag type roller turret may practically be considered to be effected by only the adjustment of the positions of the rollers in the rotating direction of the turret body, that is, by only the adjustment of the angular pitch of the rollers.
In the sense described above, the terms xe2x80x9cangular pitch adjustment of the rollersxe2x80x9d and xe2x80x9cadjustment of angular intervals between the adjacent rollersxe2x80x9d are applicable to the spur or face roller gear in meshing encagement with the worm or the dwelling portion of the globoidal or barrel cam, and to the zigzag type roller turret in meshing engagement with the plate cam unit.
The present method of manufacturing a roller turret, which includes an angular pitch adjusting step of adjusting the angular pitch of adjacent ones of the rollers by rotating the roller shafts each having the mutually eccentric roller support and stud portions, makes it possible to eliminate an error in the angular pitch of the rollers, which may result from various errors such as: an error in the positions of the mounting holes formed in the turret body, in the rotating direction of the turret body; a misalignment between the axis of rotation of the turret body when the mounting holes are formed by machining, and the axis of rotation of the turret body as incorporated in the cam index device; a dimensional error of the components associated with the rollers; and a runout of bearings supporting the rollers. Namely, the present method eliminates the angular pitch error of the rollers, which is derived from all possible factors except out-of-roundness of the rollers and misalignment of the axis of each roller and the axis of the corresponding roller shaft. The present method makes it possible to reduce the angular pitch error of the rollers, without having to enhance the dimensional and positional accuracies of the mounting holes, the dimensional accuracies of the roller shafts, rollers and the related components on the roller gear, and without having to use high-precision bearings for supporting the roller gear. Further, the present method eliminates a need of press-fitting the roller shafts into the mounting holes, which requires difficult and cumbersome control of the dimensions of the roller shafts and the mounting holes. Thus, the present method permits economical manufacture of the roller gear with a high degree of angular pitch accuracy of the rollers. Although the instant method requires the angular pitch adjustment step, the method as a whole permits an improvement in the angular pitch of the rollers of the roller gear, while reducing the cost of manufacture of the roller gear.
It is noted that the present invention was made in an effort to economically manufacture a high-precision roller turret whose angular pitch error is held within xc2x110 seconds. Although the manufacture of the high-precision roller turret having such an extremely high degree of angular pitch accuracy is desirable, the present method is also applicable to the manufacture of a roller turret having an ordinary angular pitch accuracy. According to the present invention, such an ordinary roller turret can be manufactured even if the dimensional and positional accuracies of the mounting holes formed in the turret body and the accuracy of the bearings supporting the roller turret are considerably low. The roller shaft inevitably suffers from a displacement within the mounting hole due to a gap or clearance between the stud portion of the roller shaft and the mounting hole, if the roller shaft is rotatably fitted in the mounting hole at its stud portion. For manufacturing a roller turret having an extremely high degree of angular positioning accuracy, it is required to position the roller shaft in the preliminary assembling step such that the stud portion is held in close contact with a predetermined circumferential portion of the inner circumferential surface of the mounting hole, as in the following mode (2) of this invention, such that the axis of the stud portion is slightly offset from the centerline of the mounting hole in the radial direction of the mounting hole. However, where the required angular positioning accuracy of the roller turret can be achieved in the presence of some amount of gap or clearance between the stud portion and the mounting hole, it is not essential to position the roller shaft such that the stud portion is held in close contact with the predetermined circumferential portion of the inner circumferential surface of the mounting hole.
Where the angular pitch adjustment step is implemented while the roller turret is in engagement with the roller turret cam, as described below, it is necessary to fix the roller shafts to the turret body in the preliminary assembling step, in order to prevent displacement of the roller shafts due to a relatively small load which acts on the roller shafts in the angular pitch adjustment step. However, the angular pitch adjusting step may be implemented without engagement of the roller turret with the roller turret cam, by utilizing an optical measuring device or an image processing device. IN this case, the roller shafts need not be fixed to the turret body. For instance, images of the two adjacent rollers of the spur roller gear are taken, and the distance between the same predetermined points on the two adjacent rollers (for example, on the pitch circle of the rollers) is measured. The measured distance is compared with the nominal value to calculate an error. One of the two adjacent roller shafts is rotted so as to adjust the distance to the nominal value, for thereby adjusting the angular interval between the two adjacent rollers.
(2) A method according to the above mode (1), wherein the preliminary assembling step comprises positioning each roller shaft such that the stud portion is held in close contact with a predetermined portion of an inner circumferential surface of a corresponding one of the mounting holes, and the fixing step comprises filling a gap between an outer circumferential surface of the stud portion and the inner circumferential surface, with a filler material.
With the stud portion of each roller shaft being held in close contact with the predetermined circumferential portion of the inner circumferential surface of the mounting hole, the roller shaft can be accurately positioned even in the presence of some amount of clearance or gap between the stud portion and the mounting hole. For instance, a setscrew may be provided in the turret body, so as to be movable toward a centerline of each mounting hole, so that the stud portion of the roller shaft is forced with a movement of the setscrew, onto the predetermined circumferential portion of the inner circumferential surface of the mounting hole. Thus, the stud portion can be positioned in the radial direction of the mounting hole and fixed in the mounting hole, by tightening the setscrew, so that the roller shaft is prevented from being displaced even when some amount of load acts on the roller shaft. The use of the setscrews for fixing the roller shafts to the turret body is effective to prevent displacement of the rollers in the angular pitch adjusting step wherein the roller turret is rotated in meshing engagement with the roller turret cam. This rotation of the roller turret in the angular pitch adjusting step may be effected after the angular interval adjustment is completed for some of the rollers by rotating the corresponding roller shafts, that is, before the adjustment is completed for all of the rollers. The angular pitch adjustment can be implemented for selected ones of the rollers and can be repeated for the same rollers, by loosening and tightening the corresponding setscrews, so that all angular intervals between the adjacent rollers can be adjusted to the nominal angular pitch value. Further, the use of the setscrews provide easy and economical means for provisionally fixing the roller shafts to the turret body. After the angular pitch adjusting step is completed, the gap between the stud portion of each roller shaft and the corresponding mounting hole is filled with the filler material, to prevent displacement of the stud portion within the mounting hole, and to maintain a high degree of angular pitch accuracy of the roller turret.
(3) A method according to the above mode (2), wherein the filler material is an adhesive agent for bonding the stud portion to the turret body.
In the above mode of the method, an adhesive agent is used as the filler material for filling the gap between the stud portion of each roller shaft and the corresponding mount hole, so that the roller shaft is firmly bonded to the inner circumferential surface of the mounting hole. As a result, the rigidity of each roller shaft is improved, and the roller turret maintains a high degree of angular pitch accuracy with high stability.
(4) A method according to any one of the above modes (1)-(3), wherein the angular pitch adjusting step comprises: assembling the preliminary roller turret assembly and a roller turret cam having a dwelling portion such that the preliminary roller turret assembly meshes with the dwelling portion; rotating the roller turret cam and detecting a plurality of angular positions of the roller turret assembly at which the roller turret assembly is in meshing engagement with the dwelling portion of the roller turret cam; and rotating the roller shafts to adjust angular intervals between adjacent ones of the plurality of angular positions, to adjust each of the angular intervals to a nominal value of the angular pitch of the plurality of rollers.
The roller turret cam indicated above may be a globoidal cam, a barrel cam or a plate cam unit, for instance. The globoidal and barrel cams are cams having a rib which includes a dwelling portion for establishing the angular positions of the roller turret. The plate cam unit is a cam not having a rib.
The roller turret cam may be a cam which is operated or used in combination the roller turret, or a master roller turret cam which is used for the sole purpose of implementing the angular pitch adjusting step during manufacture of the roller turret in question. The use of the master roller turret cam is effective particularly where the roller turret is operated or used in combination with a roller turret cam which does not have a dwelling portion, or in combination with a worm.
The angular pitch of the rollers of the roller turret can be adjusted to the nominal value, by adjusting all angular intervals between the adjacent angular positions of the roller turret to the nominal value of the angular pitch. Accordingly, the method according to the above mode (4) permits the roller turret to have a high degree of angular pitch accuracy and therefore a high degree of angular positioning or indexing accuracy, in any of the following cases: where the roller turret is combined with a roller turret cam to provide a roller turret cam index device; where the roller turret in the form of a spur roller gear or a face roller gear is combined with a double enveloping worm or a cylindrical worm, to provide a roller turret type rotary motion transmitting device; and where the roller turret in the form of a spur roller gear or a face roller gear is combined with a globoidal or barrel cam not having a dwelling portion, to provide a spur roller gear type rotary motion transmitting device or a face roller gear type rotary motion transmission device.
By effecting the angular pitch adjusting step while the roller turret is in meshing engagement with a roller turret cam having a dwelling portion, the roller turret can be stopped at a plurality of angular positions which are established by engagement of the dwelling portion of the roller turret cam with respective pairs of the adjacent rollers of the roller turret, without accurately controlling the angular positions at which the roller turret cam is stopped. The angular pitch of the rollers of the roller turret can be easily adjusted by eliminating a deviation of each of the actually detected angular intervals between the adjacent angular positions of the roller turret, with respect to the nominal angular pitch value.
(5) A roller turret comprising: a turret body having a plurality of mounting holes formed therein such that the mounting holes are arranged in a rotating direction of the turret body; a plurality of roller shafts each including a roller support portion and a stud portion eccentric with respect to the roller support portion and fitted in a corresponding one of the plurality of mounting holes; a plurality of rollers rotatably mounted on the roller support portions of the plurality of roller shafts, respectively; and fixing means provided for each of the mounting holes, for fixing the stud portion of the corresponding roller shaft to the turret body, at a desired angular position of the corresponding roller shaft.
The angular pitch of the rollers of the roller turret can be adjusted by rotating the roller shafts, so that the roller turret has a high degree of angular pitch accuracy. After the angular pitch of the rollers has been adjusted, each roller shaft is fixed to the turret body by the fixing means, so as to prevent deterioration of the angular pitch accuracy due to rotation or inclination of the roller shaft due a load acting thereon.
(6) A roller turret according to the above mode (5), wherein the fixing means includes a plurality of setscrews provided for the plurality of roller shafts, respectively, each of the setscrews being disposed in the turret body such that each setscrew is movable toward a centerline of a corresponding one of the mounting holes, in a direction intersecting said centerline, for forcing the stud portion of the corresponding roller shaft onto an inner circumferential surface of the corresponding mounting hole.
Only one setscrew is provided for each of the mounting holes. Alternatively, two or more setscrews may be provided for each mounting hole. For example, there are provided an inner setscrew for contacting the stud portion of the corresponding roller shaft, and an outer setscrew in series with the inner setscrew. In this case, the outer setscrew functions as a lock screw for locking the inner setscrew after the stud portion is fixed in the mounting hole by the inner setscrew. Alternatively, a plurality of setscrews may be arranged in parallel, that is, spaced apart from each other in the axial direction of the stud portion, so that the stud portion is fixed at two axial positions by the two setscrews.
The fixing means including the setscrews permits the roller shafts to be selectively fixed to the turret body or released from the turret body to permit rotation of the roller shafts, as needed, so that the angular pitch adjustment procedure can be repeated until the angular interval between the adjacent rollers is adjusted to the desired value (nominal pitch value). Namely, the setscrew for the appropriate roller shaft is first loosened, the roller shaft is then rotated to adjust the angular interval between the adjacent rollers in question, and the setscrew is finally tightened to fix the roller shafts to the turret body. These steps are repeated until the angular interval has been adjusted as needed.
The setscrews used as the fixing means in the above mode (6) of the present invention may be replaced by a combination of a radially outwardly extending flange which is formed on the stud portion of each roller shaft and which is has a through-hole formed therethrough in the axial direction of the roller shaft, and a headed screw which extends through the through-hole of the flange and which is screwed into a tapped hole formed in the turret body, so that the roller shaft is fixed by the headed screw to the turret body. The through-hole is preferably an arcuate elongate hole extending along a circular arc whose center lines on the axis of the stud portion. For positioning the roller shaft in the radial direction, at least a part of the stud portion may be a tapered part which is engageable with a tapered portion of the mounting hole. The tapered part of the stud portion has a diameter which decreases in the axial direction from the roller support portion toward a distal end of the stud portion, and the tapered portion of the mounting hole has a taper angle corresponding to that of the tapered part of the stud portion, so that the tapered part of the stud portion is engageable with the tapered portion of the mounting hole. For positioning the roller shaft in the axial direction as well as in the radial direction, the roller shaft may include a radially outwardly extending flange portion so that the flange portion is held in abutting contact with a surface of the turret body. The tapered part of the stud portion and the tapered portion of the mounting hole may be provided where the fixing means includes the setscrews described above.
(7) A roller turret according to the above mode (5) or (6), wherein the fixing means includes a filler material for filling a gap between an outer circumferential surface of the stud portion and an inner circumferential surface of the corresponding mounting hole, so that the roller turret is fixed by the filler material to the turret body at the stud portion.
Between the outer circumferential surface of the stud portion of each roller shaft and the inner circumferential surface of the corresponding mounting hole, there is left a gap or clearance which permits the roller shaft to be rotated. With this gap being filled with the filler material, the roller shaft is fixed to the turret body. Unlike a screw, the filler material does not permit repeated fixing and releasing of the roller shaft to and from the turret body. However, the filler material filling the gap assures firm fixing of the roller shaft to the turret body. Where the fixing means includes both the setscrew and the filler material for each roller shaft, the setscrew may be used for provisionally fixing the roller shaft, while the filler material may be used for permanently fixing the roller shaft. The fixing means may include the filler material and a screw other than the setscrew, such as a headed screw.
Even where the fixing means does not include a setscrew or a headed screw, the roller shaft may be provisionally fixed to the turret body after the angular pitch adjustment is completed after the gap indicated above is filled with the filler material. For instance, the roller shaft may be provisionally fixed in the mounting hole at the predetermined angular position, owing to a force of friction between the stud portion and the mounting hole. To this end, the stud portion of the roller shaft may have a tapered part whose diameter decreases in the axial direction from the roller support portion toward a distal end of the stud portion. In this case, the mounting hole has a tapered portion having a taper angle corresponding to that of the tapered part of the stud portion, so that the tapered part of the stud portion is engageable with the tapered portion of the mounting hole, for provisionally fixing the roller shaft to the turret body at the desired angular position, owing to the force of friction between the tapered surfaces of the stud portion and the mounting hole.
(8) A roller turret according to the above mode (7), wherein the filler material is an adhesive agent for bonding the stud portion to the turret body.
The above mode (8) of the invention has the same advantage as the mode (3) described above with respect to the manufacturing method.
(9) A roller turret according to any one of the above modes (6)-(8), wherein the roller shaft has an abutting surface which faces in an axial direction of the roller shaft from the roller support portion toward a distal end of the stud portion, and the stud portion has a tapered surface which is inclined such that a distance between the tapered surface and the distal end of the stud portion in an axial direction of the stud portion decreases in a radially outward direction of the stud portion, each setscrew being held in engagement with the tapered surface for holding the abutting surface in abutting contact with a surface of the turret body which faces in an axial direction of the roller shaft from the distal end of the stud portion toward the roller support portion.
The abutting surface of the roller shaft may be provided on the stud portion or the roller support portion. In either of these cases, the end face of the stud portion or roller support portion may be used as the abutting surface. Alternatively, the abutting surface may be provided on an intermediate portion of the roller shaft located between the stud portion and the roller support portion.
With the setscrew held in engagement with the tapered surface of the stud portion, the roller shaft is axially moved toward the bottom of the mounting hole, due to an axial component of a force which is applied from the setscrew to the tapered surface. As a result, the abutting surface is held in abutting contact with the turret body. In addition, the stud portion is forced onto the inner circumferential surface of the mounting hole, by a radial component of the force acting on the tapered surface. Thus, the roller shaft is positioned by the setscrew and the abutting and tapered surfaces, in both the axial and radial directions.
(10) A roller turret according to the above mode (9), wherein the stud portion includes an axially intermediate part which has an annular groove formed in an outer circumferential surface thereof, the tapered surface consisting of one of opposite surfaces defining the annular grove.
In the above mode (10), the setscrew engages one of the opposite surfaces which defines the annular groove formed in the outer circumferential surface of the axially intermediate part of the stud portion, so that the stud portion is pushed in the radial direction onto the inner circumferential surface of the mounting hole, and is axially displaced toward the bottom of the mounting hole. Thus, the roller shaft can be smoothly axially moved for engagement of the abutting surface with the surface of the turret body, without an inclination relative to the centerline of the mounting hole. Further, since the tapered surface is provided by one of the opposite surfaces of the annular groove, the setscrew is engageable with the tapered surface irrespective of the angular position of the stud portion, that is, irrespective of the angular position of the roller shaft which has been rotated to adjust the angular pitch of the rollers.
(11) A roller turret according to the above mode (9) or (10), wherein the roller support portion has a larger diameter than the stud portion, and the abutting surface consists of a shoulder surface between the roller support portion and the stud portion.
The roller shaft constructed according to the above mode (11) wherein the shoulder surface between the roller support portion and the stud portion functions as the abutting surface is relatively simple in configuration and is accordingly economical to manufacture. However, the abutting surface may be provided by a radially outwardly extending flange portion formed between the roller support portion and the stud portion, more precisely, by one of opposite surfaces of the flange portion which is on the side of the stud portion. In this arrangement, the diameter of the roller support portion may be made equal to or even smaller than that of the stud portion. Therefore, this arrangement is desirable where the distance between the adjacent rollers is relatively small.
(12) A roller turret according to any one of the above modes (9)-(11), wherein each setscrew has a tapered end face engageable with the tapered surface of the stud portion.
In the above mode (12) wherein the setscrew has the tapered end face, the surface area of contact of the setscrew with the tapered surface of the stud portion of the roller shaft can be made relatively large, permitting the roller shaft to be fixed to the turret body with a relatively large force.
(13) A roller turret according to any one of the above modes (9)-(12), further comprising a thrust piece interposed between the abutting surface of the roller shaft and the surface of the turret body, so that the abutting surface is held in abutting contact with the surface of the turret body through the thrust piece.
The thrust piece provided according to the above mode (13) is suitably used in the roller turret according to the above mode (11). In this case, the thrust piece having a diameter larger than the inside diameter of the roller is disposed between the surface of the turret body and the abutting surface which is formed between the roller support portion and the stud portion. Where the diameter of the thrust piece is smaller than the outside diameter of the roller, only a radially inner portion of the roller is in frictional contact with the thrust piece during operation of the roller turret, so that the friction resistance between the roller and the thrust piece is reduced.
(14) A roller turret according to any one of the above modes (7)-(13), wherein the turret body has a filler passage formed for each of the plurality of mounting holes, the filler passage being open at one of opposite ends thereof in an outer surface of the turret body and at the other end to the corresponding mounting hole.
The filler material is injected through the filler passage to fill the gap between the outer circumferential surface of the stud portion of the roller shaft and the inner circumferential surface of the mounting hole.
(15) A roller turret according to the above mode (7) or (8), wherein the stud portion of each roller shaft has an annular groove formed in the outer circumferential surface, and the turret body has a filler passage formed for each of the plurality mounting holes, the filler passage being open at one of opposite ends thereof in an outer surface of the turret body and at the other end to a portion of the corresponding mounting hole which is substantially aligned with the annular groove in the stud portion in an axial direction of the stud portion.
The annular groove promotes the delivery of the filler material in the circumferential direction of the stud portion, around the stud portion, assuring the filling of the entirety of the gap between the outer circumferential surface of the stud portion and the inner circumferential surface of the mounting hole.
(16) A roller turret according to the above mode (15), wherein the roller shaft has an abutting surface which faces in an axial direction of the roller shaft from the roller support portion toward a distal end of the stud portion, and the fixing means includes a plurality of setscrews provided for the plurality of roller shafts, respectively, each of the setscrews being disposed in the turret body such that each setscrew is movable toward a centerline of a corresponding one of the mounting holes, in a direction intersecting said centerline, the annular groove being defined by opposite surfaces one of which is a tapered surface which is inclined such that a distance between the tapered surface and the distal end of the stud portion in a axial direction of the stud portion decreases in a radially outward direction of the stud portion, each setscrew being held in engagement with the tapered surface for holding the abutting surface of the roller shaft in abutting contact with a surface of the turret body which faces in an axial direction of the roller shaft from the distal end of the stud portion toward the roller support portion.
The annular groove which serves to deliver the filler material into the above-indicated gap provides the tapered surface with which the setscrew is engageable. Accordingly, it is not necessary to form another annular groove for providing the tapered surface for the setscrew, in addition to the annular groove for delivering the filler material. The annular groove is preferably located in an axially intermediate part of the stud portion.
(17) A roller turret according to any one of the above modes (14)-(16), wherein the turret body has at least one air breather passage which is open at one of opposite ends thereof to an atmosphere and at the other end to the corresponding mounting hole.
The at least one air breather passage permits air to be discharged therethrough from the mounting hole, and facilitates the delivery of the filler material into the mounting hole, more precisely, into the gap between the outer circumferential surface of the stud portion and the inner circumferential surface of the mounting hole, so that the gap is more stably filled with the filler material.
(18) A roller turret according to the above mode (17), wherein the at least one air breather passage includes an air breather hole which is open at the other end to a portion of the corresponding mounting hole which is near a bottom of the corresponding mounting hole.
Since the air is discharged from the mounting hole through the air breather hole, the filler material can easily flow toward the bottom of the mounting hole.
(19) A roller turret according to the above mode (17) or (18), wherein the at least one air breather passage includes at least one air breather groove formed in at least one of (a) an abutting surface formed on the roller shaft so as to face in an axial direction of the roller shaft from said roller support portion toward a distal end of the stud portion, and (b) a surface of the turret body which is in abutting contact with the abutting surface.
Since the air is discharged from the mounting hole through the air breather groove, the filler material can easily flow toward the open end of the mounting hole.
(20) A roller turret according to the above mode (7) or (8), wherein at least one of (a) an intermediate part of the outer circumferential surface of the stud portion and (b) an intermediate part of the inner circumferential surface of the mounting hole which corresponds to the intermediate part of the outer circumferential surface has an annular groove, and the turret body has a communication hole which communicates at one of opposite ends thereof with the annular groove and is open at the other end in an outer surface of the turret body, the annular groove and the communication hole cooperating to define a filler passage for filling the gap with the filler material, and wherein at least one of the turret body and the roller shaft has an annular recessed portion communicating with an open end of the mounting hole, and further has a first air passage which communicates at one of opposite ends thereof with the annular recessed portion and is open at the other end thereof to an atmosphere, and the turret body has a second air passage which is open at one of opposite ends thereof to a bottom portion of the mounting hole and at the other end thereof to the atmosphere, the first and second air passages providing an air breather passage for permitting air to be discharged from the mounting hole.
The air present in a portion of the above-indicated gap between the annular groove and the open end of the mounting hole is discharged into the atmosphere through the annular recessed portion and the first air passage, permitting easy flow of the filler material into that portion of the gap. The annular recessed portion communicating with the entirety of the circumference of the gap permits the air to be discharged from the entire circumferential portion of the gap through the first air passage. If the first air passage were closed by the filler material before the air around the entire circumference of the stud portion is discharged, the air could not be discharged smoothly through the first air passage. To prevent this drawback, the first air passage preferably communicates with the annular recessed portion, at a circumferential position at which the corresponding circumferential portion of the gap can be filled with the filler material with most difficulty. On the other hand, the air in the other portion of the gap between the annular groove and the bottom of the mounting hole is discharged into the atmosphere through the second air passage. A space defined by the bottom of the mounting hole and the distal end face of the stud portion communicates with the entire circumferential portion of the gap, and therefore permits the air to be discharged from the entire circumferential portion of the gap through the second air passage. Thus, the above form (20) of the invention assures adequate filling of the gap with the filler material.
(21) A roller turret according to the above mode (7) or (8), wherein the turret body has a filler passage for filling the gap with the filler material, the filler passage being open at one of opposite ends thereof to an atmosphere and at the other end thereof to a bottom portion of the mounting hole, and at least one of the roller shaft and the turret body has at least one air breather passage which is open at one of opposite ends thereof to an open end of the mounting hole and at the other end thereof to the atmosphere.
The filler material is injected into the above-indicated gap through the bottom portion of the mounting hole. The air breather passage facilitates the flow of the filler material from the bottom portion of the mounting hole toward the open end portion.
(22) A roller turret according to the above mode (21), wherein the at least one air breather passage includes an annular recessed portion communicating with the open end of the mounting hole, and a communication passage which communicates at one of opposite ends thereof to the annular recessed portion and is open at the other end thereof to the atmosphere.
The above description on the annular recessed portion and the first air passage in the above mode (20) applies to the annular recessed portion and the communication passage in the above mode (22).
(23) A roller turret according to any one of the above modes (5)-(22), wherein each of the plurality of roller shafts carries two mutually concentric rollers mounted on the roller support portion such that the two mutually concentric rollers are rotatable independently of each other.
In the roller turret according to the above mode (23), one of the two rollers (referred to as xe2x80x9cdouble-roller assemblyxe2x80x9d) rotatably mounted on each roller shaft is adapted to engage one of opposite surfaces of a groove defined by two portions of a rib of a globoidal or barrel cam or a tooth of a worm, which two portions are spaced apart from each other in the axial direction of the cam or worm, while the other of the two rollers is adapted to engage the other of the opposite surfaces of the groove. The engagement of the two rollers with the surfaces of the groove takes place without a clearance therebetween, so that there does not exist a backlash therebetween at any angular position of the cam or worm. Where only one roller is mounted on the roller shaft, some clearance must be provided between the outer circumferential of the roller and the opposite surfaces of the groove, for permitting the roller to pass the groove, so that some backlash is inevitably left between the roller and the groove. In the present roller turret wherein the two rollers of the double-roller assembly on each roller shaft are adapted to engage the respective two different surfaces defining the groove. In this arrangement wherein a clearance is provided between each of the two rollers and one of the two surfaces of the groove, the double-roller assembly as a whole does not have a clearance with respect to the groove. Further, one of the two rollers of the double-roller assembly may be arranged to engage, without a clearance, the other surfaces of the rib of the cam or tooth of the tooth of the worm, which surfaces do not contribute to defining the groove. Thus, the present arrangement permits smooth rolling contact of the rollers with the surfaces of the rib or tooth of the cam or worm, without a backlash, at all angular positions of the cam or worm. The roller turret according to the above mode (23) is suitably used for a device which is required to operate with reduced operating vibration and noise. Namely, the present roller turret may be combined with a globoidal cam, a barrel cam or a worm, to provide a globoidal cam index device, a barrel cam index device, a spur roller gear type rotary motion transmitting device, or a face roller gear type rotary motion transmitting device, which assures high degrees of motion transmitting accuracy and angular positioning or indexing accuracy, and significantly reduced operating vibration and noise.
However, the complete elimination of the backlash is not essential in the above mode (23) of the invention, provided the backlash is not larger than 8xcexc or 5xcexc. Where the single-roller assembly is used, a considerably large amount of clearance must be provided between the roller and the groove, to permit the roller to smoothly pass the groove, in the presence of dimensional errors of the roller and the groove.
(24) A method of manufacturing a roller turret cam index device including a roller turret cam and a roller turret which engage each other such that the roller turret cam and the roller turret are rotatable about respective two axes that are spaced apart from each other and intersect each other, the method comprising: a step of preparing a turret body having a plurality of mounting holes formed therein such that the mounting holes are arranged in a rotating direction of the turret body; a step of preparing a plurality of roller shafts each including a roller support portion on which the roller is rotatably mounted, and a stud portion which is eccentric with respect to the roller support portion; a preliminary roller turret assembling step of preparing a preliminary roller turret assembly wherein each of the roller shafts is rotatably fitted at the stud portion in a corresponding one of the mounting holes; a preliminary index device assembly step of preparing a preliminary index device, by assembling the preliminary roller turret assembly and the roller turret cam within a housing; an angular pitch adjusting step of adjusting an angular pitch of adjacent ones of the plurality of rollers of the preliminary roller turret assembly, by rotating the roller shafts; and a fixing step of fixing all of the roller shafts to the turret body after the angular pitch adjusting step.
In the roller turret cam index device manufactured by the method according to the above mode (24) of this invention, the roller turret cam may be a globoidal cam or a barrel cam, for example, while the roller turret may be a spur roller gear or a face roller gear, for example.
The present method permits economical manufacture of the roller turret cam index device which has a high degree of angular positioning or indexing accuracy owing to the angular pitch adjustment of the rollers by rotating the roller shafts.
(25) A method according to the above mode (24), wherein the angular pitch adjusting step comprises: attaching a rotation angle detector to the housing, for detecting an angle of rotation of the preliminary roller turret assembly; rotating the roller turret cam to rotate the preliminary roller turret assembly; detecting angular positions of the preliminary roller turret assembly at which the preliminary roller turret assembly is in meshing engagement with a dwelling portion of the roller turret cam, on the basis of output signals of the rotation angle detector; and rotating the roller shafts such that each of angular intervals between adjacent ones of the angular positions is adjusted to a nominal value of the angular pitch.
The angular intervals between the adjacent angular positions of the preliminary roller turret assembly can be readily detected by the output signals of the rotation angle detector attached to the housing of the device to detect the angle of rotation of the preliminary roller turret assembly. The angular pitch of the preliminary roller turret assembly can be established by rotating the roller shafts such that each of the angular intervals between the adjacent angular positions of the roller turret is equal to the nominal angular pitch value.
(26) A method according to the above mode (24), wherein the angular pitch adjusting step comprises rotating the roller turret cam to rotate the preliminary roller turret assembly, by an electric motor which is connected to the roller turret cam and whose angles of rotation in opposite directions can be controlled.
The roller turret cam can be readily rotated by a desired angle, by the electric motor connected thereto, so that the angular pitch adjustment is facilitated. For instance, the electric motor is commanded, by a worker or operator, to be operated to rotate the roller turret cam by an angle necessary for rotating the roller turret by an angle corresponding to the nominal angular pitch, so that the roller whose roller shaft is to be rotated to adjust the angular interval engages the roller turret cam. The electric motor is then commanded by the worker to be operated to rotate the roller turret cam by an angle necessary for rotating the preliminary roller turret assembly to bring the roller in question whose roller shaft is to be rotated, to a predetermined angular pitch adjusting position of the preliminary roller turret assembly at which the roller shaft carrying the roller in question is rotated to adjust the angular interval. After the angular interval adjustment is completed for the roller in question, the electric motor is operated in the reverse direction to rotate the roller turret cam to return the preliminary roller turret assembly to the angular position at which the roller in question engages the roller turret cam. Alternatively, the electric motor is commanded by the worker to be operated to rotate the roller turret cam by the number of revolutions necessary for rotating the preliminary roller turret assembly so that all of the rollers successively engage the dwelling portion of the roller turret cam. In this case, the angular positions of the preliminary roller turret assembly at which the individual rollers engage the dwelling portion of the roller turret cam are automatically detected.
(27) A roller turret cam index device including a roller turret cam and a roller turret which engage each other such that the roller turret cam and the roller turret are rotatable about respective two axes that are spaced apart from each other and intersect each other, wherein the roller turret comprises: a turret body having a plurality of mounting holes formed therein such that the mounting holes are arranged in a rotating direction of the turret body; a plurality of roller shafts each including a roller support portion and a stud portion eccentric with respect to the roller support portion and fitted in a corresponding one of the plurality of mounting holes; a plurality of rollers rotatably mounted on the roller support portions of the plurality of roller shafts, respectively; and fixing means provided for each of the mounting holes, for fixing the stud portion of the corresponding roller shaft to the turret body, at a desired angular position of the corresponding roller shaft.
The roller turret cam index device according to the above mode (27) has the same advantages as described above with respect to the roller turret according to the above mode (5).
The present roller turret cam index device is simpler in construction than an index device which uses a coupling device including coupling members for improved indexing accuracy of the index device. The present roller turret cam index device is advantageous in the indexing speed over the index device using the coupling device wherein the coupling members must perform engaging and releasing actions for each indexing action.
In the present roller turret cam index device, the roller turret may be rotated in a predetermined one direction or in opposite directions, and may have a single indexing pitch or two or more different indexing pitch values. A typical example of the roller turret cam index device according to the above mode (27) is an intermittently indexing device wherein the roller turret cam has a single dwelling portion, and the rollers provided on the roller turret sequentially engages the rib of the roller turret cam each time the roller turret cam is rotated through 360xc2x0, so that the roller turret is intermittently rotated in the predetermined one direction at the predetermined angular pitch. However, the roller turret cam may have a plurality of indexing portions, which may consist of or include indexing portions (helical portions) which are inclined in opposite directions. Further, the roller turret cam index device may be adapted such that changing of the rollers which engage the rib of the roller turret cam takes place two or more times during one full revolution of the roller turret cam, or such that the roller turret is rotated in the opposite directions within an angular range less than 360xc2x0 of the roller turret. In the later case, the rollers need not be arranged along the entire circumference of the roller turret. Any roller turret having three or more rollers may be used in the present roller turret cam index device, which can be so called in a broad sense.
(28) A roller turret cam index device according to the above mode (27), wherein each of the plurality of roller shafts carries two mutually concentric rollers rotatably mounted on the roller support portion such that the two mutually concentric rollers are rotatable independently of each other, and the roller turret cam includes a rib having two portions which are spaced apart from each other in an axial direction of the roller turret cam and which have respective two opposite surfaces defining a groove therebetween, the two opposite surfaces of the groove being shaped such that one of the two rollers mounted on each roller shaft is engageable with one of the two opposite surfaces while the other of the two rollers is engageable with the other of the two opposite surfaces.
In the roller turret cam index device according to the above mode (28), the amount of backlash between the roller and the groove of the roller turret cam is made smaller (not larger than 5xcexc) than in the roller turret cam index device wherein only one roller is mounted on each roller shaft of the roller turret, as described above with respect to the above mode (23) of the invention. The backlash may be even eliminated. With the backlash being extremely small or eliminated, the roller turret cam index device can operate under a strict operating condition, with reduced vibration and noise.
(29) A method of manufacturing a roller turret type rotary motion transmitting device including a worm and a roller turret which engage each other such that the roller turret cam and the roller turret are rotatable about respective two axes that are spaced apart from each other and intersect each other, wherein the roller turret comprises: a step of preparing a turret body having a plurality of mounting holes formed therein such that the mounting holes are arranged in a rotating direction of the turret body; a step of preparing a plurality of roller shafts each including a roller support portion on which the roller is rotatably mounted, and a stud portion which is eccentric with respect to the roller support portion; a preliminary roller turret assembling step of preparing a preliminary roller turret assembly wherein each of the roller shafts is rotatably fitted at the stud portion in a corresponding one of the mounting holes; an angular pitch adjusting step of (a) installing the preliminary roller turret assembly in a jig equipped with a master roller turret cam which is identical with the worm except in that the master roller turret cam has a rib including a dwelling portion, (b) rotating the master roller turret cam to rotate the preliminary roller turret assembly, (c) detecting angular positions of the preliminary roller turret assembly at which the preliminary roller turret assembly is in meshing engagement with the dwelling portion of the master roller turret cam, and (d) rotating the roller shafts such that each of angular intervals between adjacent ones of the angular positions is adjusted to a nominal value of the angular pitch; a fixing step of fixing all of the roller shafts to the turret body after the angular pitch adjusting step, whereby the roller turret is prepared; and assembling the roller turret and the worm within a housing, to obtain the roller turret type rotary motion transmitting device.
The roller turret type rotary motion transmitting device manufactured by the method according to the above mode (29) of this invention may be a spur roller gear type rotary motion transmitting device or a face roller gear type rotary motion transmitting device. These rotary motion transmitting devices fall within the rotary motion transmitting device in a broad sense, and may be classified into a rotary motion transmitting device in a narrow sense, a speed reduction and a speed increasing device.
The roller turret type rotary motion transmitting device may serve as a roller turret type speed reducing device where the worm is used as an input device while the roller turret is used as an output device. In the speed reducing device, the ratio of the rotating speed of the roller turret as the output speed to the rotating speed of the worm as the input speed is smaller than one. Alternatively, the roller turret type rotary motion transmitting device may serve as a roller turret type speed increasing device where the roller turret is used as the input device while the worm is used as the output device. In the speed increasing device, the ratio of the rotating speed of the worm as the output speed to the rotting speed of the roller turret as the input speed is larger than one. Where the worm has a multiple-start thread or tooth (number of starts is two or more), the worm has a relatively large lead, and a rotary motion of the worm is transmitted to the roller turret at a speed ratio of one. Thus, the roller turret type rotary motion transmitting device (in a broad sense) serves as a rotary motion transmitting device in a narrow sense.
The use of the master roller turret cam having a dwelling portion to implement the angular pitch adjusting step permits easy positioning of the preliminary roller turret assembly at the angular positions determined by engagement of the rollers with the dwelling portion. The angular pitch of the preliminary roller turret assembly can be readily adjusted by rotating the roller shafts so that each of the actually detected angular intervals between the adjacent angular positions of the preliminary roller turret assembly is equal to the nominal value of the angular pitch. The roller turret whose angular pitch has been adjusted by using the jig equipped with the master roller turret cam is removed from the jig, and is assembled with the worm within the housing of the roller turret type rotary motion transmitting device. In this assembling step, there arises some degree of assembling error, which is generally negligibly small. The assembling error can be minimized where the bearings eventually incorporated in the rotary motion transmitting device to rotatably support the roller turret are installed in the jig together with the preliminary roller turret assembly. In this case, the roller turret installed in the rotary motion transmitting device does not suffer from an indexing error due to runout of the bearings, and assures a further improvement in its indexing accuracy.
(30) A roller turret type rotary motion transmitting device including a worm and a roller turret which engage each other such that the roller turret cam and the roller turret are rotatable about respective two axes that are spaced apart from each other and intersect each other, wherein the roller turret comprises: a turret body having a plurality of mounting holes formed therein such that the mounting holes are arranged in a rotating direction of the turret body; a plurality of roller shafts each including a roller support portion, and a stud portion which is eccentric with respect to the roller support portion; a plurality of rollers rotatably mounted on the roller support portions of the plurality of roller shafts, respectively; and fixing means provided for each of the mounting holes, for fixing the stud portion of the corresponding roller shaft to the turret body, at a desired angular position of the corresponding roller shaft.
The roller turret type rotary motion transmitting device according to the above mode (30) has the same advantage as described above with respect to the above mode (5), and can serve as a spur roller gear type or face roller gear type rotary motion transmitting device in a broad sense, which has a high degree of rotary motion transmitting accuracy.
(31) A roller turret type rotary motion transmitting device according to the above mode (30), wherein each of the plurality of roller shafts carries two mutually concentric rollers rotatably mounted on the roller support portion such that the two mutually concentric rollers are rotatable independently of each other, and the roller turret cam includes a rib having two portions which are spaced apart from each other in an axial direction of the roller turret cam and which have respective two opposite surfaces defining a groove therebetween, the two opposite surfaces of the groove being shaped such that one of the two rollers mounted on the each roller shaft is engageable with one of the two opposite surfaces while the other of the two rollers is engageable with the other of the two opposite surfaces.
In the roller turret type rotary motion transmitting device according to the above mode (31), the amount of backlash between the roller and the groove of the worm is made smaller (not larger than 5xcexc) than in the roller turret type rotary motion transmitting device wherein only one roller is mounted on each roller shaft of the roller turret, as described above with respect to the above mode (23) of the invention. The backlash may be even eliminated. With the backlash being extremely small or eliminated, the roller turret type rotary motion transmitting device can operate under a strict operating condition, with reduced vibration and noise.
(32) A roller turret type rotary motion transmitting device according to the above mode (30) or (31), further including a housing body, a bearing, and a bearing housing supported by the housing body, and wherein the roller turret further comprises a turret shaft which is rotatable with the turret body and rotatably supported by the bearing housing through the bearing such that radial and axial movements of the turret shaft and inclination of the turret shaft in all directions relative to the bearing housing are prevented, and wherein the turret body, the turret shaft, the bearing and the bearing housing constituting a sub-assembly which is removably mounted on the housing body.
In the roller turret type rotary motion transmitting device according to the above mode (32) wherein the turret body, the turret shaft, the bearing and the bearing housing constitute a sub-assembly, these components of the sub-assembly can be easily built in an assembling jig equipped with a master roller turret cam having a dwelling portion, so that those components are assembled into the sub-assembly and the angular pitch of the adjacent rollers carried by the turret body is adjusted. After the assembling operation using the assembling jig, the sub-assembly is removed from the jig, and is then mounted on the housing body of the rotary motion transmitting device. After the angular pitch adjustment of the rollers is completed, there is no need to disassemble the sub-assembly into the components, in order to assemble those components in the housing body of the rotary motion transmitting device. The present arrangement wherein the turret body, the turret shaft, the bearing and the bearing housing constitute the sub-assembly is free from deterioration of the angular pitch accuracy of the rollers due to a misalignment of the axis of the turret shaft of the roller turret relative to the bearing housing, which would arise if the turret body, turret shaft, bearing and bearing housing are disassembled after the angular pitch adjustment of the rollers using the assembling jig and are re-assembled in the housing body to obtain the rotary motion transmitting device. Although those components may be disassembled after the angular pitch adjustment and re-assembled in the housing body of the rotary motion transmitting device, the rollers can be protected from deterioration of the angular pitch accuracy, according to the present arrangement which permits the sub-assembly to be mounted on the housing body without disassembling after the angular pitch adjustment using the assembling jig. Namely, a high degree of accuracy of the angular pitch of the rollers established by the adjustment using the jig can be maintained in the rotary motion transmitting device.
In the present roller turret type rotary motion transmitting device according to the above mode (32), the turret shaft is supported by the bearing at one axial end portion thereof. However, the turret shaft may be supported by a bearing at the other axial end portion. The bearing which is one of the components of the above-indicated sub-assembly and which is disposed at one axial end portion of the turret shaft functions to establish alignment of the turret shaft (turret body) relative to the housing body of the rotary motion transmitting device in the radial and axial directions. It will be understood that an auxiliary bearing may be provided for supporting the turret shaft at the other axial end portion, when the turret shaft is subject to a relatively large load and has a relatively large mount of elastic deformation. The principle of this invention covers the provision of this auxiliary bearing.
(33) A roller turret type rotary motion transmitting device according to claim 30, wherein each of the plurality of roller shafts rotatably carries a corresponding one of the plurality of rollers, and the worm has a plurality of ribs defining a plurality of grooves, each of the grooves being defined by two opposite surfaces of adjacent ones of the ribs, the two opposite surfaces being shaped such that each of the rollers is engageable with one of the two opposite surfaces but is not engageable with the other of the two opposite surfaces.
It is desirable to increase the number of the ribs of the worm as the speed ratio of the worm and the roller turret approaches xe2x80x9c1xe2x80x9d (1/1). When the speed ratio is equal to xe2x80x9c1xe2x80x9d, for example, the worm desirably has twelve ribs. Where the number of ribs which simultaneously engage the roller turret is xe2x80x9c4xe2x80x9d or larger, for example, only one roller supported on each roller shaft is sufficient provided at least every other rib (every second rib) of the four or more ribs is shaped such that it does not contact the two adjacent rollers on its opposite sides. In this arrangement, each roller which contacts one of the two adjacent ribs does not contact the other of these two adjacent ribs. Typically, at least every other rib of all of the initially shaped ribs is further shaped to have recessed portions in its opposite surfaces. These ribs which have the recessed portions and which do not contact the rollers do not perform any function with respect to the rollers, and merely exist between the ribs which function to transmit a rotary motion from the worm to the roller turret through the rollers. Accordingly, those ribs having the recessed portions may be entirely removed.
(34) A parallel cam index device including a plate cam unit and a zigzag type roller turret which engage each other such that the plate cam unit and the zigzag type roller turret are rotatable about respective two axes that are spaced apart from each other and are parallel to each other, the plate cam unit including a first plate cam and a second plate cam which are concentric with each other and rotatable together, and the zigzag type roller turret including a first roller turret portion and a second roller turret portion which are concentric with each other and rotatable together, the first and second turret portions including a first and a second group of rollers, respectively, the rollers of the first and the roller of the second groups being arranged alternately in a rotating direction of the zigzag type roller turret such that the rollers of the first group and the rollers of the second group are alternately located at respective two axial positions of the roller turret, the rollers of the first group engaging the first cam plate while the roller of the second group engaging the second plate cam, wherein each of the first and second roller turret portions comprises: a turret body having a plurality of mounting holes formed therein such that the mounting holes are arranged in the rotating direction of the zigzag type roller turret; a plurality of roller shafts each including a roller support portion on which a corresponding one of the rollers is rotatably mounted, and a stud portion which is eccentric with respect to the roller support portion and fitted in a corresponding one of the plurality of mounting holes; and fixing means provided for each of the mounting holes, for fixing the stud portion of the corresponding roller shaft to the turret body, at a desired angular position of the corresponding roller shaft.
The turret body of the zigzag type roller turret may consist of a single plate member or a plurality of plate members. Where the turret body consists of a single plate member, the single plate member may be constructed to have a plurality of mounting holes formed along a circle having a center at the axis of rotation of the roller turret, and the roller shafts are fitted at their stud portions in the respective mounting holes such that the roller support portions of the roller shafts extend alternately in the opposite axial directions of the plate member (turret body). The rollers are rotatably mounted on the roller support portions of the roller shafts, so that the rollers are alternately located at respective two axial positions of the turret body. In this arrangement, the single plate serves as both the turret body of the first roller turret portion and the turret body of the second roller turret portion. Where the turret body of the zigzag type roller turret consists of a plurality of plate members, for example, three plate members, these three plate members are arranged in parallel with each other and spaced apart from each other in the axial direction of the roller turret. The roller shafts carrying the rollers of the first group are supported at their opposite ends by an intermediate one of the three plate members and one of the two outer plate members, while the roller shafts carrying the rollers of the second group are supported at their opposite ends by the intermediate plate member and the other of the two outer plate members. In this arrangement, the intermediate plate member cooperates with one and the other of the two outer plate members to constitute the first and second roller turret portions, respectively.
In the present parallel cam index device, the angular pitch of the zigzag type roller turret can be adjusted by rotating the roller shafts, so that the index device assures a high degree of angular positioning or indexing accuracy.
It is to be understood that the features of the above modes (5) through (23) may be provided in or applied to the method of manufacturing a roller turret according to any one of the above modes (1)-(4), a method of manufacturing a roller turret cam index device according to any one of the above modes (24)-(26), a roller turret type cam index device according to the above mode (27) or (28), a method of manufacturing a roller turret type rotary motion transmitting device according to the above mode (29), a roller turret type rotary motion transmitting device according to the above mode (30) or (33), and a parallel cam index device according to the above mode (34).